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Moment Measurements

One of the present authors has extensively used the dipole-moment method to calculate conformational equilibria of saturated heterocycles. In hindsight this has been a frustrating experience not so much because of the assumptions and approximations that must be made, but because the results in some cases are in good agreement with those derived from other methods, whereas for other groups of compounds the dipole-moment conclusions are clearly incorrect. In this discussion we first discuss the method, using piperidines as an example, and then attempt to assess its areas of applicability and causes of failure. [Pg.39]

A general account of dipole-moment measurements and the use of these in conformational analysis has been given.3 At the University of East Anglia, for a study of the conformational equilibria of piperidines,119 121 electronic polarizations were estimated from tabulated bond polarizations122 (neglecting contributions of atomic polarization to the total polarization) or determined from refractive-index measurements. Most measurements were carried out in benzene or cyclohexane. [Pg.39]

Oxirane has a higher boiling point (10.5°) than cyclopropane (—32.9°), which indicates its more polar character. Its dipole moment has been determined by numerous authors via the dielectric constant (e.g.. Refs. ) and the Stark effect. The results agree well 1.9D. The structures of aryl-substituted oxiranes have also been determined by means of dipole moment measurements.  [Pg.13]


The magnitude of this moment measures the extent that the distribution is skewed in one direetion or another in referenee to the mean. [Pg.680]

In dioxane solution at 30°C, content of IH tautomer is 60 10% according to dipole moment measurements (80JHC1373). [Pg.190]

Roughly speaking, the first moment, t, measures the size of a residence time distribution, while higher moments measure its shape. The ability to characterize shape is enhanced by using moments about the mean ... [Pg.544]

Electric dipole moment measurements on R3SiCo(CO)4, (R3Si)2Fe(CO)4, and related compounds have indicated a relationship between v(CO) and charge transfer in the Si—M bond within a given series the central transition metal is apparently not charged 156). Application of the relationship to HjSiCo(CO)4 suggests a small bond dipole in the sense... [Pg.288]

Conformation problems in five- and six-membered rings containing phosphorus continue to attract attention and, using n.m.r., i.r., and dipole-moment measurements, studies have been reported on 1,3,2-dioxaphospholan systems (118), > 1,3,2-dioxaphosphorinane systems... [Pg.119]

The geminal coupling of some azo1ooxaphospho1enes is reported to correlate with A.. 9 1 Vicinal couplings have been used in the conformational analysis of a variety of compounds such as dioxaphosphorinanes,92 phosphorinanes (in combination uith CNDO/2 calculations),93 and bromophosphorinanes (in combination uith dipole moment measurements).99 The various couplings for 1,1-viny1idene-diphosphonic acid and its salts have also been measured.95... [Pg.403]

Projection theorem, electric dipole moment measurement, 244—245 P,T-odd interactions ... [Pg.286]

This condition can be met by choosing either a RHSE of a sufficiently large radius, or by maintaining a high speed of rotation. From the results of the turning moment measurements shown in Fig. 4, one may take Re = 200 as the lower limit where the boundary layer approximation is valid. Thus the useful flow regime for electrochemical application is ... [Pg.189]

This moment measures the extent and direction of the shift of an atom s electronic charge cloud with respect to the nucleus. The quantity M(fi) can effectively be regarded as an intra-atomic dipole moment. The intra-atomic dipole moment of each atom contributes to the... [Pg.154]

Of special interest (see Table II) is the structure of compound XVI, obtained in a reaction with thermodynamic control, and its sulfide (XVII), as both molecules contain the P—H bond. Infrared, Raman, and NMR studies as well as dipole moment measurements showed that the P—H bond was axial in these compounds. In some cases the conclusions of NMR and dipole moment studies were verified by X-ray single-crystal analysis. [Pg.70]

In this next section the dipole magnitude and directionality from MM3(2000) is compared to results obtained by MM3(96), Hartree-Fock and Mdller-Plesset minimized structures (calculated using GAUSSIAN94),77 as well as experimental dipole moment measurements.78 For the molecular mechanics geometry optimizations, full matrix energy minimizations were carried out, and ground state structures were verified by the vibrational... [Pg.51]

Magnetic susceptibility measurements have been made for the lanthanide complexes of 2,6-DMePyO (171), EPO, BPO, EAsO, BAsO (237, 238), and AAP (95). In all these cases, the measured magnetic susceptibilities agree with the free ion values. Dipole moment measurements have been carried out on complexes of the type Ln(TBP)3-(N03)3 (387, 388). ESR studies on Gd(AP)6 I3 (389) and thermal decomposition studies on the complexes of the lanthanides with DMSO (250), DPSO (250, 259), QNO (175), HOQNO (190), 18-crown-6 (132), 15-crown-5 (131), and gycine (390) have also been reported. [Pg.202]

X-ray analysis of 4,4-dimethylandrostan-3-on-17/3-yl benzoate (67) that the A ring is in a deformed chair conformation (225) in the crystal, and NMR and dipole moment measurements show the same to be true in solution. [Pg.155]


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Moment measures

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